Sunday, October 05, 2008

On Test: SMC Pentax-A 28mm f/2.8



After testing four Vivitar 28mm lenses in the search for the Perfect Normal some might ask what is so special about Vivitar that other manufacturers couldn't also manage? In particular, Pentax themselves are known for lens quality throughout almost their entire range. In order to provide a baseline I thought it best to throw into the test group the SMC Pentax-A 28mm f/2.8. This lens was released in 1984 and so is a more recent design than the others I have looked at. However, it is similar enough to earlier Pentax offerings.

How does Pentax compare with third-party Vivitar? Read on to find out.

This lens is not that different from the earlier M line. It is composed of 7 elements in 7 groups with 5 aperture blades and an aperture range of f/2.8 to f/22. The minimum focus distance is 30 cm. The filter size is a convenient 49 mm and weight is only 170g. It is commonly available from second-hand stores at £60, a bit cheaper than that from individual sellers. The build of the lens is good with solid metal, knurled barrel and smooth focus. Unlike the Vivitars I have tested, this lens is auto-aperture and so does not require stop-down metering.

SMC Pentax-A 28mm f/2.8 -- front

My copy is in good condition with typical signs of use. Testing proceeded the same way as before, with four shots being taken at each of three distances. A generic metal wide-angle hood in order to reduce glare. The only difference is that I shot in aperture-priority mode instead of manual.

SMC Pentax-A 28mm f/2.8 -- barrel

(I should have dusted before taking these photos of the lens itself -- sorry!)

Minimum Focus Distance

f/2.8
A28 min f/2.8
f/4
A28 min f/4
f/8
A28 min f/8
f/16
A28 min f/16

At Two Feet

f/2.8
A28 24in f/2.8
f/4
A28 24in f/4
f/8
A28 24in f/8
f/16
A28 24in f/16

At Infinity

f/2.8
A28 infinity f/2.8
f/4
A28 infinity f/4
f/8
A28 infinity f/8
f/16
A28 infinity f/16

Conclusions

I will leave it to yourself to click through these images and compare them at 100%. I find that only at f/8 does the lens really shine, though you can't say it is crappy anywhere. But certainly it does not jump off the screen as being superior to the Vivitar lenses. In fact, the feeling I get from it is of a more grainy, nervous disposition. Images do not capture the detail I would like and seem somehow "rough"... perhaps relating to low-level detail. Maybe this lens works better on film cameras than digital? (This is a complex topic beyond explication by myself.)

Colours too seem muted and I did not have the same latitude to "push" them when processing.

Here are some real-world results, which look fine at this size.

Garlic Flower
Garlic Flower

Parking Surface
Parking Surface

Flag Of Convenience
Flag Of Convenience

I should note that there is a faster Pentax-A f/2.0 lens, but this is quite (extremely?) rare and would be expensive if found today.

What you can take from this is the lesson that any of these lenses can produce decent images. However, I am completely happy to sell on this lens and use the best of the Vivitars instead.

Speaking of which, I have one more on its way to me now. That will be the last lens I test in this series. Stay tuned!

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1 comment:

Miserere said...

I also recently acquired this lens to have as a baseline, but haven't had time to use it thoroughly. I'm curious to see how it will stack up against its 3rd party contenders.

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